This invention relates to transmission of a load from a load carrier (container, bridge) to a load measuring transducer and further to a foundation, without the influence of disturbing loads. Load measuring transducers are load measuring sensing means in electromechanical scales, i.e., scales in which an electrical signal is used which corresponds to the measure of the load.
When using load measurinng transducers to measure a load, the influence of disturbing loads is a central problem. The problem exists because the load carrier is affected by the disturbance as the the load causes deformation of the carrier. The deformation is reflected in changes both in the length and the angles of the carrier. Dimensional changes can also be caused by other influences such as variations in temperature. Those transversal movements and angular changes create additional forces and movements which act on points of support including those on the load measuring transducers. To eliminate disturbing influences, attempts have been made either to make the load measuring transducers stiff so that they can transmit the disturbing forces and movements, or resilient; in either case, the arrangement is made such that no erroneous measuring indication of the load would arise. Because disturbing loads can substantially exceed the size of the measuring load, those solutions can lead to constructions which are uneconomical at great loads or which are unreliable.
A number of methods according to the above-mentioned solutions are known. Resilient transmissions are advantageous in that they are self-stabilizing, i.e., that they tend to enter a starting position. In that manner, no strut is needed to hold the load carrier in a distinct position.
Examples of such constructions are described in Swedish Patent No. 386 268 wherein the load measuring transducer is provided with spherical end surfaces having a radius greater than half the height of the load measuring transducer; that arrangement gives rise to a self-stabilizing effect. Moreover, that device is embodied so that the transversal movements and angular movements are limited by mechanical stops. Other examples of resilient constructions are described in Swedish Patents 366 116 and 451 891. Those constructions are provided with cylindrical oscillating pieces placed above the load measuring transducer and have spherical end surfaces; they avoid errors which arise in the load measuring transducers due to their angular changes from the vertical axis upon transversal movements of the load carrier.
However, with spherical surfaces, great mechanical stress concentrations appear on the contact surfaces. If the radii of the spherical surfaces are increased to reduce stress concentrations, the working point of the contact surface of the load measuring means is moved in proportion to the angular change of the oscillating piece or load measuring transducer; errors which certainly arise (according to one patent) can be used to compensate for weaknesses of the load measuring transducer. Therefore, the size of stress concentrations cause restrictions in the size of the resetting force relative to the measuring load. Those restrictions bring demands on precision when arranging the load carrier on load measuring transducers, and on work adjustments to ensure that the oscillating means have a stable vertical starting position.